Patent Application
20240410375
The present disclosure relates to a centrifugal fan.
A centrifugal fan, which is used in a blower, has been previously proposed. In the previously proposed centrifugal fan, a skew angle of a trailing edge of a blade is smaller than a skew angle of a leading edge of the blade. With this configuration, this centrifugal fan reduces noise and improves pressure boosting characteristics by limiting a secondary flow vortex generated in the airflow flowing in a flow passage formed between corresponding adjacent two blades which are adjacent to each other in a rotational direction. The skew angle is an angle defined between a main plate and a line, which connects between a portion of the blade joined to the main plate and a portion of the blade joined to a shroud, at a negative pressure surface side of the blade.
This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
According to one aspect of the present disclosure, a centrifugal fan includes a shroud, a main plate and a plurality of blades. The plurality of blades are arranged at predetermined intervals in a rotational direction between the shroud and the main plate and are joined to the shroud and the main plate. A tangent line, which is tangent to a positive pressure surface of a predetermined blade among the plurality of blades and passes through a trailing edge of the predetermined blade, is defined as a first tangent line. A virtual circle is centered on a rotational axis and passes through the trailing edge of the predetermined blade, and a tangent line, which is tangent to the virtual circle and passes through the trailing edge of the predetermined blade, is defined as a second tangent line. Among a plurality of angles defined between the first tangent line and the second tangent line, an angle, which is placed in front of the first tangent line in the rotational direction and is on an outer side of the virtual circle relative to the second tangent line, is defined as an outlet angle. When a change in the outlet angle is viewed at each of a plurality of locations axially arranged along the trailing edge, the trailing edge has at least one inflection point where an increase or decrease in the outlet angle is changed.
The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.
A centrifugal fan, which is used in a blower, has been previously proposed. In the previously proposed centrifugal fan, a skew angle of a trailing edge of a blade is smaller than a skew angle of a leading edge of the blade. With this configuration, this centrifugal fan reduces noise and improves pressure boosting characteristics by limiting a secondary flow vortex generated in the airflow flowing in a flow passage (hereinafter, referred to as an inter-blade passage) formed between corresponding adjacent two blades which are adjacent to each other in a rotational direction. The skew angle is an angle defined between a main plate and a line, which connects between a portion of the blade joined to the main plate and a portion of the blade joined to a shroud, at a negative pressure surface side of the blade.
The centrifugal fan used in the blower may possibly have variations in an airflow velocity distribution of the airflow discharged from a blade outlet depending on a shape or a size of each component, such as the shroud, the main plate and the blades. When the variations in the airflow velocity distribution of the airflow discharged from the blade outlet becomes large in the centrifugal fan, the noise is increased, and the air blowing efficiency is deteriorated. Therefore, the previously proposed centrifugal fan has room for further improvement.
According to one aspect of the present disclosure, a centrifugal fan includes a shroud, a main plate and a plurality of blades. The shroud is shaped in a ring form and has an air suction port at a center of the shroud. The main plate is opposed to the shroud and is configured to be rotated together with the shroud. The plurality of blades are arranged at predetermined intervals in a rotational direction between the shroud and the main plate and are joined to the shroud and the main plate. A tangent line, which is tangent to a positive pressure surface of a predetermined blade among the plurality of blades and passes through a trailing edge of the predetermined blade, is defined as a first tangent line. A virtual circle is centered on a rotational axis and passes through the trailing edge of the predetermined blade, and a tangent line, which is tangent to the virtual circle and passes through the trailing edge of the predetermined blade, is defined as a second tangent line. Among a plurality of angles defined between the first tangent line and the second tangent line, an angle, which is placed in front of the first tangent line in the rotational direction and is on an outer side of the virtual circle relative to the second tangent line, is defined as an outlet angle. When a change in the outlet angle is viewed at each of a plurality of locations axially arranged along the trailing edge, the trailing edge has at least one inflection point where an increase or decrease in the outlet angle is changed. At least one of the outlet angle, which is measured at a corresponding adjacent one of the plurality of locations adjacent to the main plate along the trailing edge, and the outlet angle, which is measured at a corresponding adjacent one of the plurality of locations adjacent to the shroud along the trailing edge, is smaller than the outlet angle, which is measured at a corresponding one of the plurality of locations where the outlet angle is the largest among the plurality of locations axially arranged along the trailing edge.
According to the above aspect, there are three possible configurations. The first configuration is that the outlet angle measured at the corresponding adjacent location of the trailing edge adjacent to the main plate and the outlet angle measured at the corresponding adjacent location of the trailing edge adjacent to the shroud are both made relatively small. The second configuration is that the outlet angle measured at the corresponding adjacent location of the trailing edge adjacent to the main plate is made relatively small. The third configuration is that the outlet angle measured at the corresponding adjacent location of the trailing edge adjacent to the shroud is made relatively small.
In the description of the present disclosure, the adjacent location of the trailing edge adjacent to the main plate is defined as a location of the trailing edge that is on the main plate side of the inflection point which is closest to the main plate. Furthermore, the adjacent location of the trailing edge adjacent to the shroud is defined as a location of the trailing edge that is on the shroud side of the inflection point which is closest to the shroud.
The first configuration (i.e., the configuration in which the outlet angle measured at the corresponding adjacent location of the trailing edge adjacent to the main plate and the outlet angle measured at the corresponding adjacent location of the trailing edge adjacent to the shroud are both made relatively small) is effective in a case where the airflow velocity in the shroud side region and the airflow velocity in the main plate side region at the blade outlet are both low, and the airflow velocity in an axial center region of the blade outlet is high in a hypothetical structure where the trailing edge is formed parallel to the rotational axis. The airflow velocity in the main plate side region of the blade outlet may possibly become low due to an influence of a boundary layer generated by, for example, friction between the airflow and the main plate. Furthermore, the airflow velocity in the shroud side region of the blade outlet may possibly become low due to an influence of, for example, a vortex generated near the shroud in the inter-blade passage. In such a case, when the outlet angle, which is measured at the corresponding adjacent location of the trailing edge adjacent to the shroud, and the outlet angle, which is measured at the corresponding adjacent location of the trailing edge adjacent to the main plate, are both made relatively small, the airflow velocity in these regions are accelerated in comparison to the other regions at the trailing edge. In addition to this, by increasing the outlet angle, which is measured at a location of the axial center portion of the trailing edge, the airflow velocity at the region of the axial center portion can be decelerated in comparison to the other regions at the trailing edge. Therefore, with the centrifugal fan described above, the airflow velocity distribution of the airflow discharged from the blade outlet can be made closer to uniform, and thereby it is possible to reduce the noise and improve the air blowing efficiency.
The second configuration (i.e., the configuration in which the outlet angle measured at the corresponding adjacent location of the trailing edge adjacent to the main plate is made relatively small) is effective in a case where the airflow velocity in the main plate side region of the blade outlet is low in the hypothetical structure where the trailing edge is formed parallel to the rotational axis. In such a case, when the outlet angle, which is measured at the corresponding adjacent location of the trailing edge adjacent to the main plate, is made relatively small, the amount of work applied from the main plate side portion of the blade to the airflow is increased, and thereby the airflow velocity in the main plate side region is accelerated in comparison to the other regions at the trailing edge. Therefore, with the centrifugal fan described above, the airflow velocity distribution of the airflow discharged from the blade outlet can be made closer to uniform, and thereby it is possible to reduce the noise and improve the air blowing efficiency.
The third configuration (i.e., the configuration in which the outlet angle measured at the corresponding adjacent location of the trailing edge adjacent to the shroud is made relatively small) is effective in a case where the airflow velocity in the shroud side region of the blade outlet is low in the hypothetical structure where the trailing edge is formed parallel to the rotational axis. In such a case, when the outlet angle, which is measured at the corresponding adjacent location of the trailing edge adjacent to the shroud, is made relatively small, the amount of work applied from the shroud side region of the blade to the airflow is increased, and thereby the airflow velocity in the shroud side region is accelerated in comparison to the other regions at the trailing edge. Therefore, with the centrifugal fan described above, the airflow velocity distribution of the airflow discharged from the blade outlet can be made closer to uniform, and thereby it is possible to reduce the noise and improve the air blowing efficiency.
Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each of the following embodiments, portions, which are the same or equivalent to each other, will be indicated by the same reference signs. With respect to the drawings referenced in the respective embodiments, a shape of each component, a size of each component, the number of blades, and a thickness of each blade in a centrifugal fan are described schematically for the sake of clarity of explanation and do not limit the present disclosure.
A first embodiment will be described with reference to the drawings. A centrifugal fan of the first embodiment is used in a blower of, for example, an air conditioning apparatus or a ventilating apparatus.
As shown in
The shroud 2 is shaped in a ring form and has the air suction port 21 which is configured to suction the air and is formed at a center of the shroud 2. The shroud 2 is shaped such that the shroud 2 progressively approaches the other axial side as the shroud 2 extends from the air suction port 21 toward the radially outer side.
The main plate 3 is shaped in a circular disk form and progressively approaches the other axial side as the main plate 3 extends from the center portion toward the radially outer side. In other words, the main plate 3 is formed such that the center portion of the main plate 3 projects toward the air suction port 21. A shaft of an electric motor (not shown) is installed to the center portion of the main plate 3.
The blades 4 are arranged at predetermined intervals in a rotational direction of the centrifugal fan 1 between the main plate 3 and the shroud 2. A portion 41 of each blade 4, which is placed on the one side in the axial direction, is joined to the shroud 2, and a portion 42 of each blade 4, which is placed on the other side in the axial direction, is joined to the main plate 3. That is, the blades 4, the shroud 2 and the main plate 3 are formed integrally in one-piece. Each of the blades 4 is arranged such that a trailing edge 45 of the blade 4 is placed behind (i.e., on a backward side of) a virtual plane that includes the rotational axis CL and a leading edge 46 of the blade 4 in the rotational direction. Therefore, the centrifugal fan 1 is a turbofan.
The centrifugal fan 1 (i.e., the main plate 3, the shroud 2 and the blades 4) is rotated by the electric motor (not shown) in the rotational direction indicated by an arrow in, for example,
As shown in
In contrast, as shown in
Now, an outlet angle at the trailing edge 45 of the blade 4 will be described with reference to
As shown in
In
The centrifugal fan 1 of the first embodiment is configured to have the at least one inflection point POI at the trailing edge 45 of each blade 4. Furthermore, this centrifugal fan 1 is configured such that the outlet angle θ3, which is measured at the adjacent location of the trailing edge 45 adjacent to the main plate 3, and the outlet angle θ1, which is measured at the adjacent location of the trailing edge 45 adjacent to the shroud 2, are both smaller than the outlet angle θ2 which is measured at the location of the axial center portion 453 of the trailing edge 45. The significance of the above configuration of the centrifugal fan 1 of the present embodiment will be described hereinafter.
As shown in
In
In the centrifugal fan of the comparative example, as indicated by arrows FL1, FL2, FL3 in
Therefore, in the centrifugal fan of the comparative example, as indicated by arrows FL4 to FL8 and a dot-dot-dash line, variations occur in the airflow velocity distribution of the airflow discharged from the blade outlet 44. Thus, the noise may possibly be increased, and the pressure boosting characteristics may possibly be deteriorated.
In contrast,
The blades 4 of the centrifugal fan 1 of the first embodiment have the above-described configuration. That is, the trailing edge 45 has the at least one inflection point POI, and the outlet angle θ3, which is measured at the adjacent location of the trailing edge 45 adjacent to the main plate 3, and the outlet angle θ1, which is measured at the adjacent location of the trailing edge 45 adjacent to the shroud 2, are both smaller than the outlet angle θ2 which is measured at the location of the axial center portion 453 of the trailing edge 45. In other words, the outlet angle θ2, which is measured at the location of the axial center portion 453 of the trailing edge 45, is larger than the outlet angle θ3, which is measured at the adjacent location of the trailing edge 45 adjacent to the main plate 3, and the outlet angle θ1, which is measured at the adjacent location of the trailing edge 45 adjacent to the shroud 2. By increasing the outlet angle, the force, which is applied from the blade 4 to the airflow flowing in the inter-blade passage 43, tends to be reduced, and thereby the amount of work applied from the blade 4 to the airflow is reduced to reduce the airflow velocity in comparison to the other regions. Therefore, in the first embodiment, as indicated by an arrow FL10 and a dot-dot-dash line, by increasing the outlet angle θ2 measured at the location of the axial center portion 453 of the trailing edge 45, the airflow velocity at the axial center region of the inter-blade passage 43 can be decelerated in comparison to the other regions at the trailing edge 45. Thus, the centrifugal fan 1 of the first embodiment can provide the more uniform airflow velocity distribution of the airflow discharged from the blade outlet 44.
Furthermore, in the centrifugal fan 1 of the first embodiment, the outlet angle θ3 at the adjacent location of the trailing edge 45 adjacent to the main plate 3 is small, as described above. With this configuration, the force is more likely applied from the blade 4 to the airflow in the inter-blade passage 43, and thereby the amount of work applied from the blade 4 to the airflow is increased to increase the airflow velocity in comparison to the other locations. Therefore, in the first embodiment, as indicated by an arrow FL12, by reducing the outlet angle θ3, which is measured at the adjacent location of the trailing edge 45 adjacent to the main plate 3, the airflow velocity, which is relatively low in the region adjacent to the main plate 3 at the inter-blade passage 43, can be accelerated in comparison to the other regions at the trailing edge 45. Thus, the centrifugal fan 1 of the first embodiment can provide the more uniform airflow velocity distribution of the airflow discharged from the blade outlet 44.
Next, with reference to
As shown in
In
Now, a negative pressure surface side outlet angle at the blade 4 will be described with reference to
As shown in
In
Next, with reference to
As shown in
In
Each of the blades 4 of the centrifugal fan 1 of the present embodiment is shaped so that the negative pressure surface side outlet angle and the positive pressure surface side outlet angle are different from each other, and the negative pressure surface side blade surface angle and the positive pressure surface side blade surface angle are different from each other. With this configuration, it is possible to limit the detachment of the airflow at the negative pressure surface 48 and also to adjust the amount of work applied from the blade 4 to the airflow at the positive pressure surface 47, and thereby the airflow velocity distribution of the airflow in the inter-blade passage 43 can be made closer to uniform.
The centrifugal fan 1 of the first embodiment described above implements the following actions and effects.
(1) The centrifugal fan 1 of the first embodiment has the at least one inflection point POI, at which the increase or decrease in the outlet angle is changed, at the trailing edge 45 of the blade 4. Furthermore, the outlet angle θ3, which is measured at the adjacent location of the trailing edge 45 adjacent to the main plate 3, and the outlet angle θ1, which is measured at the adjacent location of the trailing edge 45 adjacent to the shroud 2, are both smaller than the outlet angle θ2 which is measured at the location of the trailing edge 45 where the outlet angle is the largest.
According to this configuration, the centrifugal fan 1 described above is effective in a case where the airflow velocity in the shroud 2 side region and the airflow velocity in the main plate 3 side region at the blade outlet 44 are both low, and the airflow velocity in the axial center region of the blade outlet 44 is high in the hypothetical structure where the trailing edge 45 is formed parallel to the rotational axis CL. In this case, in the centrifugal fan 1 of the first embodiment, the outlet angle θ1, which is measured at the adjacent location of the trailing edge 45 adjacent to the shroud 2, and the outlet angle θ3, which is measured at the adjacent location of the trailing edge 45 adjacent to the main plate 3, are both made small, and thereby the airflow velocity in these regions are accelerated in comparison to the other region(s) at the trailing edge 45. Furthermore, by increasing the outlet angle θ2 which is measured at the location of the axial center portion 453 of the trailing edge 45, the airflow velocity at the region of the axial center portion 453 can be decelerated in comparison to the other regions at the trailing edge 45. Therefore, with the centrifugal fan 1 of the first embodiment, the airflow velocity distribution of the airflow discharged from the blade outlet 44 can be made closer to uniform, and thereby it is possible to reduce the noise and improve the air blowing efficiency.
(2) In the centrifugal fan 1 of the first embodiment, the blade surface angle θ6, which is measured at the adjacent location of the blade 4 adjacent to the main plate 3 at the predetermined position P1, and the blade surface angle θ4, which is measured at the adjacent location of the blade 4 adjacent to the shroud 2 at the predetermined position P1, are smaller than the blade surface angle θ5, which is measured at the corresponding location of the blade 4 at the predetermined position P1 where the blade surface angle is the largest among the plurality of locations axially arranged along the blade 4 at the predetermined position P1.
According to this configuration, even for the airflow in the inter-blade passage 43, by changing the amount of work applied from the blade 4 to the airflow, the detachment of the airflow from the blade surface can be limited, and the airflow velocity distribution can gradually become uniform starting from the upstream side of the blade outlet 44.
The configuration of changing the blade surface angle from the middle of the blade 4 between the leading edge 46 and the trailing edge 45 and its actions and effects are the same in the second to eleventh embodiments described below.
(3) Each of the blades 4 of the centrifugal fan 1 of the first embodiment is shaped so that the negative pressure surface side outlet angle and the positive pressure surface side outlet angle are different from each other, and the negative pressure surface side blade surface angle and the positive pressure surface side blade surface angle are different from each other.
With this configuration, it is possible to limit the detachment of the airflow at the negative pressure surface 48 and also to adjust the amount of work applied from the blade 4 to the airflow at the positive pressure surface 47, and thereby the airflow velocity distribution of the airflow discharged from the blade outlet 44 can be made closer to uniform. The configuration described above and its actions and effects are the same in the second to eleventh embodiments described below.
Next, a second embodiment will be described. The second embodiment is a modification where the shape of the trailing edge 45 of each blade 4 is changed from that of the first embodiment, and the rest of the second embodiment is the same as that of the first embodiment. Therefore, only the parts different from those of the first embodiment will be described in the following description.
As shown in
Furthermore, the centrifugal fan 1 of the second embodiment is also configured such that when a change in the outlet angle is viewed at each of the plurality of locations axially arranged along the trailing edge 45, the trailing edge 45 has at least one inflection point POI where an increase or decrease in the outlet angle is changed. In the second embodiment, the inflection point POI is located at the location of the axial center portion 453 of the trailing edge 45.
The centrifugal fan 1 of the second embodiment described above is configured such that the outlet angle measured at the portion (location) of the trailing edge 45 of the blade 4, which extends from the portion 451 joined to the shroud 2 to the axial center portion 453, is made large. Therefore, the centrifugal fan 1 can decelerate the high airflow velocity in the region extending from the shroud 2 to the axial center in the inter-blade passage 43 in comparison to the other region(s) in the inter-blade passage 43. In addition, the centrifugal fan 1 is configured such that the outlet angle measured at the location of the trailing edge 45 adjacent to the main plate 3 is made small. Therefore, the centrifugal fan 1 can accelerate the low airflow velocity in the region adjacent to the main plate 3 in the inter-blade passage 43 in comparison to the other region(s) in the inter-blade passage 43. Therefore, with the centrifugal fan 1, the airflow velocity distribution of the airflow discharged from the blade outlet 44 can be made closer to uniform, and thereby it is possible to reduce the noise and improve the air blowing efficiency.
Next, a third embodiment will be described. The third embodiment is a modification where the shape of the trailing edge 45 of the blade 4 is changed from that of the first embodiment, and the rest of the third embodiment is the same as that of the first embodiment. Therefore, only the parts different from those of the first embodiment will be described in the following description.
As shown in
Furthermore, the centrifugal fan 1 of the third embodiment is also configured such that when a change in the outlet angle is viewed at each of the plurality of locations axially arranged along the trailing edge 45, the trailing edge 45 has at least one inflection point POI where an increase or decrease in the outlet angle is changed. In the third embodiment, the inflection point POI is located at the location of the axial center portion 453 of the trailing edge 45.
The centrifugal fan 1 of the third embodiment described above is configured such that the outlet angle measured at the portion (location) of the trailing edge 45 of the blade 4, which extends from the portion 452 joined to the main plate 3 to the axial center portion 453, is made large. Therefore, the centrifugal fan 1 can decelerate the high airflow velocity in the region extending from the main plate 3 to the axial center in the inter-blade passage 43 in comparison to the other region(s) in the inter-blade passage 43. In addition, the centrifugal fan 1 of the third embodiment is configured such that the outlet angle at the location of the portion 451 of the trailing edge 45 adjacent to the shroud 2 is made small. Therefore, the centrifugal fan 1 can accelerate the low airflow velocity in the region adjacent to the shroud 2 in the inter-blade passage 43 in comparison to the other regions in the inter-blade passage 43. Therefore, with the centrifugal fan 1 described above, the airflow velocity distribution of the airflow discharged from the blade outlet 44 can be made closer to uniform, and thereby it is possible to reduce the noise and improve the air blowing efficiency.
Next, a fourth embodiment will be described. The fourth embodiment is a modification where the shape of the trailing edge 45 of the blade 4 is changed from that of the first embodiment, and the rest of the fourth embodiment is the same as that of the first embodiment. Therefore, only the parts different from those of the first embodiment will be described in the following description.
As shown in
The configuration of the fourth embodiment is effective in a case where a pressure dropping element located on the upstream side of the centrifugal fan 1 or the shape or physique of each corresponding component of the centrifugal fan 1 causes variations in the airflow velocity distribution in the respective regions of the blade outlet 44 in the hypothetical structure where the trailing edge 45 is formed parallel to the rotational axis CL. The pressure dropping element refers to an element, such as a case of the blower at which the centrifugal fan 1 is installed, a filter placed on the upstream side of the centrifugal fan 1, causing a pressure drop in the airflow. In such a case, even in the fourth embodiment, the outlet angle measured at the location of the trailing edge 45, at which the airflow velocity is low, is made small, and the outlet angle measured at the location of the trailing edge 45, at which the airflow velocity is high, is made large. As described above, by reducing the outlet angle, the amount of work applied from the blade 4 to the airflow can be increased, and thereby the airflow velocity can be increased in comparison to the other locations. In contrast, by increasing the outlet angle, the amount of work applied from the blade 4 to the airflow can be decreased, and thereby the airflow velocity can be decreased in comparison to the other locations. Therefore, the airflow velocity distribution of the airflow discharged from the blade outlet 44 can be made closer to uniform even in a case where the variations occur at the regions of the blade outlet 44 in the airflow velocity distribution of the airflow discharged from the blade outlet 44 in the hypothetical structure where the trailing edge 45 is formed parallel to the rotational axis CL. Therefore, with the centrifugal fan 1 of the fourth embodiment, it is possible to reduce the noise and improve the air blowing efficiency.
Next, a fifth embodiment will be described. The fifth embodiment is a modification of the fourth embodiment.
As shown in
Even with the configuration of the fifth embodiment, the airflow velocity distribution of the airflow discharged from the blade outlet 44 can be made closer to uniform even in the case where the variations occur at the regions of the blade outlet 44 in the airflow velocity distribution of the airflow discharged from the blade outlet 44 in the hypothetical structure where the trailing edge 45 is formed parallel to the rotational axis CL. Therefore, with the centrifugal fan 1 of the fifth embodiment, it is possible to reduce the noise and improve the air blowing efficiency.
Next, a sixth embodiment will be described. The sixth embodiment is a modification of the fourth or fifth embodiment.
As shown in
Even with the configuration of the sixth embodiment, the airflow velocity distribution of the airflow discharged from the blade outlet 44 can be made closer to uniform even in the case where the variations occur at the regions of the blade outlet 44 in the airflow velocity distribution of the airflow discharged from the blade outlet 44 in the hypothetical structure where the trailing edge 45 is formed parallel to the rotational axis CL. Therefore, with the centrifugal fan 1 of the sixth embodiment, it is possible to reduce the noise and improve the air blowing efficiency.
Each of seventh to eleventh embodiments is a modification where the shape of the trailing edge 45 of the blade 4 viewed in the rotational direction is changed from that of the first embodiment, and the rest of each of the seventh to eleventh embodiments is the same as that of the first embodiment. Therefore, only the parts different from those of the first embodiment will be described in the following description. Any one of the configurations of the seventh to eleventh embodiments can be combined with any one of the configurations of the first to sixth embodiments described above.
As shown in
As indicated by an arrow FL21 in
In contrast, the centrifugal fan 1 of the seventh embodiment is configured such that the amount of work applied from the main plate 3 side portion of the blade 4 to the airflow is increased, and thereby as indicated by an arrow FL23, the airflow around the blade outlet 44 can be pulled once again toward the main plate 3 at the inter-blade passage 43. Therefore, in comparison to the case of the hypothetical structure where the trailing edge 45 is formed parallel to the rotational axis CL, the airflow velocity distribution of the airflow discharged from the blade outlet 44 can be made closer to uniform, and thereby it is possible to reduce the noise and improve the air blowing efficiency.
The configuration of the centrifugal fan 1 of the seventh embodiment is more effective in a case where a relationship of 0.5<Dsi/Dso<0.7 is satisfied. Here, Dsi denotes an inner diameter of the shroud 2, and Dso denotes an outer diameter of the shroud 2. This is due to the following reasons.
In a hypothetical case where the ratio of Dsi/Dso is equal to or smaller than 0.5, it is possible to ensure the sufficient length of the inter-blade passage 43 for conducting the airflow after the occurrence of the biasing of the airflow toward the shroud 2. In this case, even when the trailing edge 45 is formed parallel to the rotational axis CL in the view taken in the rotational direction, after the occurrence of the biasing of the airflow toward the shroud 2, this biasing of the airflow is alleviated before reaching the trailing edge 45. In contrast, in another hypothetical case where the ratio of Dsi/Dso is equal to or larger than 0.7, the airflow in the inter-blade passage 43 reaches the trailing edge 45 before occurrence of biasing of the airflow that causes reattachment of the airflow to the shroud 2. In other words, the airflow indicated by the arrows FL21, FL22 is cut off in the middle. Therefore, in order to make the configuration of the centrifugal fan 1 of the seventh embodiment more useful, it is desirable that the relationship of 0.5<Dsi/Dso<0.7 is satisfied.
The centrifugal fan 1 of the seventh embodiment described above is configured such that the distance Db2, which is measured between the rotational axis CL and the portion 452 of the trailing edge 45 joined to the main plate 3, is longer than the distance Db1, which is measured between the rotational axis CL and the portion 451 of the trailing edge 45 joined to the shroud 2.
With this configuration, the amount of work applied from the main plate 3 side portion of the blade 4 to the airflow is increased, and thereby the airflow around the blade outlet 44 in the inter-blade passage 43 can be pulled once again toward the main plate 3. Therefore, in comparison to the case of the hypothetical structure where the trailing edge 45 is formed parallel to the rotational axis CL, the airflow velocity distribution of the airflow discharged from the blade outlet 44 can be made closer to uniform, and thereby it is possible to reduce the noise and improve the air blowing efficiency.
The centrifugal fan 1 of each of the eighth to eleventh embodiments described hereinafter is also configured such that the distance Db2, which is measured between the rotational axis CL and the portion 452 of the trailing edge 45 joined to the main plate 3, is longer than the distance Db1, which is measured between the rotational axis CL and the portion 451 of the trailing edge 45 joined to the shroud 2. Therefore, the centrifugal fan 1 of each of the eighth to eleventh embodiments also has the same configuration as the seventh embodiment described above with respect to the above-described point, and thus can achieve the same actions and effects as the centrifugal fan 1 of the seventh embodiment.
As shown in
The centrifugal fan 1 of the eighth embodiment described above can achieve the same actions and effects as those of the seventh embodiment.
As shown in
The centrifugal fan 1 of the ninth embodiment described above can achieve the same actions and effects as those of the seventh and eighth embodiments. The number of the corners and the number of the straight portions of the stepped form of the trailing edge 45 can be set to any number.
As shown in
The centrifugal fan 1 of the tenth embodiment described above can also achieve the same actions and effects as those of the seventh to ninth embodiments.
As shown in
The centrifugal fan 1 of the eleventh embodiment described above can also achieve the same actions and effects as those of the seventh to tenth embodiments.
In each of the embodiments described above, the centrifugal fan 1 is described as the turbofan. However, the present disclosure is not limited to this. For example, the centrifugal fan 1 may be any other type, such as a radial fan.
In each of the embodiments described above, although the configuration of the predetermined blade 4 among the plurality of blades 4 of the centrifugal fan 1 is described, the remaining two or more or all of the plurality of blades 4 of the centrifugal fan 1 may be formed in the same configuration as the configuration of the predetermined blade 4.
The present disclosure is not limited to the above embodiments, and the above embodiments may be appropriately modified. Further, the above embodiments are not unrelated to each other and can be appropriately combined unless the combination is clearly impossible. Needless to say, in each of the above-described embodiments, the elements of the embodiment are not necessarily essential except when it is clearly indicated that they are essential and when they are clearly considered to be essential in principle. In each of the above embodiments, when a numerical value such as the number, numerical value, amount, range or the like of the constituent elements of the embodiment is mentioned, the present disclosure should not be limited to such a numerical value unless it is clearly stated that it is essential and/or it is required in principle. In each of the above embodiments, when the shape, the positional relationship or the like of the constituent elements of the embodiment are mentioned, the present disclosure should not be limited the shape, the positional relationship or the like unless it is clearly stated that it is essential and/or it is required in principle.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-065872 | Apr 2022 | JP | national |
This application is a continuation application of International Patent Application No. PCT/JP2023/011994 filed on Mar. 24, 2023, which designated the U.S. and claims the benefit of priority from Japanese Patent Application No. 2022-065872 filed on Apr. 12, 2022. The entire disclosures of all of the above applications are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2023/011994 | Mar 2023 | WO |
| Child | 18810890 | US |
